3 Answers
3

\documentclass{article}
\usepackage{showframe}% http://ctan.org/pkg/showframe
\usepackage{varwidth}% http://ctan.org/pkg/varwidth
\begin{document}
Here is some text. Here is some text. Here is some text.
Here is some text. Here is some text. Here is some text.
Here is some text. Here is some text. Here is some text.
\begin{center}
​\begin{varwidth}{\textwidth}
Here is some title that is somewhat long. \par
And some notes. \\
And some more notes.
\end{varwidth}
\end{center}
Here is some text. Here is some text. Here is some text.
Here is some text. Here is some text. Here is some text.
Here is some text. Here is some text. Here is some text.
\end{document}

A width of \textwidth for the varwidth environment makes sure that the text will fit within the text block, but also shrink to the natural width of the box (in case it's not as wide).

For keeping the title centred (if the notes extend beyond the width of the title), you can use

\begin{center}
​\begin{varwidth}{\textwidth}
\centerline{Here is some title that is somewhat long.} \par
And some notes. \\
And some more notes. And some more notes. And some more notes.
\end{varwidth}
\end{center}

However, you are required to use \par to the title here then. There are other ways to do this as well.